The Study of VFTO Distribution in the Insulation System of IOCT Used in Traction Network

The FDS (Frequency-domain Dielectric Spectroscopy) of oil-immersed insulation paper, and semi-conductive paper with different moisture content, has been measured. The data measured are fitted as a function of frequency and moisture content using the amendatory Cole–Cole model utilizing the least square technique. Then, the broadband MTL model of the insulation system of IOCT (Inverted-type Oil-immersed Current Transformer) is established considering the capacitive electrodes thin layer, and the distribution parameters consider the moisture and frequency dependence. A new method for VFTO (Very Fast Transient Overvoltage) distribution calculation of insulation systems is proposed.

An evolutionary optimization approach to prevent electronics burnout in subsea oil and gas equipment

The electronics burnout in subsea engineering equipment caused by the excessive heating of electronics due to improper cooling mechanism is an area of major concern in subsea oil and gas fields. Very often the electronic canisters are encapsulated by insulation to prevent hydrate formation in the subsea completion equipment. The electronic equipment with a set of sensors is usually deployed subsea for live monitoring of data and to regulate the functioning of the equipment. This study presents a numerical methodology to predict and prevent electronics burnout in a pressure/temperature transmitter (PT/TT) that is truly representative of a wide class of PT/TT deployed subsea. An optimization study of the insulation system around the PT/TT sensors that encompasses the various contradicting constraints that are routinely encountered in subsea engineering has been presented for the benefit of the readers. In the present study, the optimal design of the insulation system around the electronics equipment is generated using a combination of thermal finite element analysis and evolutionary optimization algorithms. The results obtained show that the proposed methodology can yield results which could be a tremendous improvement in the traditional means of designing the insulation systems for such electronics equipment. It is also shown that locating the electronic housing far from the production fluid in the PT/TT sensors can lead to proper cooling and thereby avoid the burnout to a significant extent.

Designing the Insulation System for Motors in Electrified Aircraft: Optimization, Partial Discharge Issues and Use of Advanced Materials

Designing the insulation system for motors to be used in electrical aircraft requires efforts for maximizing specific power, but, in parallel, particular attention to achieve high reliability. As a major harm for organic insulation systems is partial discharges, design must be able to infer their likelihood during any operation stage and handle their potential inception. This paper proposes a new approach to carry out optimized or conservative insulation system designs which can provide the specified life at the chosen failure probability as well as look at the option of possibly reducing the risk of partial discharges to zero, at any altitude. Examples of designing turn, phase to ground and phase-to-phase insulation systems are reported, with cases where the design can be optimized and other cases where the optimized design does not pass IEC testing standard. Therefore, the limits for design feasibility as a function of the required level of safety and reliability are discussed, showing that the presence of partial discharges cannot be always avoided even through conservative design criteria. Therefore, the use of advanced, corona-resistant materials must be considered, in order to reach a higher, sometimes redundant, level of reliability.

Results of performance tests of an experimental class H insulation system for locomotive traction motors and its monitoring using the mobile diagnostics means

Objective: To perform traction electric motor performance tests with an experimental class H heat resistance insulation system. Methods: An experimental set of traction electric motors was manufactured at the Voronezh Diesel Locomotive Repair Plant to be compared with a motor of class F insulation. Results: The performance indicators of controlled locomotives have been summarized. Explanations and definition of additional insulation parameters and an example of their use in case of traction electric motor failure due to damage to controlled locomotives have been given. Practical importance: The proposed methodology for predictive diagnostics of traction electric motors performance can be used in service locomotive depots.

Kinetic Assessment of Mechanical Properties of a Cellulose Board Aged in Mineral Oil and Synthetic Ester

In oil-immersed power transformers, the insulation system is constituted of a dielectric oil–solid combination. The insulation oil generally used is mineral oil; however, this fluid has started to be substituted by natural and synthetic esters due to their higher biodegradability and flash point. The introduction of a new fluid in the insulation system of power transformers requires kinetic models that can estimate the degradation rate of insulation solids. The aim of this work was to go further in quantifying through different kinetic models the deterioration suffered by a commercial cellulose board (PSP 3055), which is one of the solid materials used in the insulation system of oil-filled transformers. The aging study was extended to cellulose board specimens immersed in two different oils (mineral and synthetic ester). It was obtained that there is a lower degradation when synthetic ester is used in the insulation system. Additionally, it can be concluded that the use of mechanical properties to quantify the degradation of the cellulose board through kinetic models provides information about the different behavior shown by PSP 3055 when different fiber direction angles are considered.

Hygrothermal performance of a brick wall with interior insulation in cold climate: Vapour open versus vapour tight approach

Interior insulation of historic buildings is well-studied in Central Europe; however, their conclusions might not be directly applicable to colder climates. Heat, air and moisture (HAM) modelling can be a valuable tool for studying those solutions in different conditions. Recently, incorporating the capillary condensation redistribution (CCR) test into the material characterization process has shown to cause dramatic improvement in correlating hygrothermal modelling results to measurements in certain situations. It is also noteworthy, that the HAM modelling errors made using material data from conventional characterization process can be severely non-conservative. In this article a parametric study of a 51 cm thick mass masonry wall is undertaken to determine the effect of the improved material properties on the reliability of a vapour open ‘capillary active’ autoclaved aerated concrete (AAC) and calcium silicate (CaSi) interior insulation solutions and to compare them to a vapour tight insulation system. A 49-year real weather dataset from Estonia is used. The results show that compared to conventionally characterized material properties the CCR-optimized material data causes more critical conditions directly behind the interior insulation, while having a similar performance in the exterior part of the masonry. The differences occur close to the performance limits and highlight the importance of using the CCR test in material characterization process. The vapour tight and vapour open systems showed a very similar impact on the freeze-thaw cycles and on the maximum ice saturation of the exterior part of the masonry. The vapour open solutions perform better than the vapour tight PIR in terms of frost damage and possible mould growth behind the insulation – even though the advantage has been reduced when using the CCR-optimized material data. Regardless of the insulation solution, a case-specific approach is still required to avoid damaging the original wall and/or the added insulation system.

Hygrothermal performance of internally insulated masonry walls with embedded wooden beam heads: a field study on the impact of hydrophobisation

Internal insulation remains often the only option to thermally upgrade massive masonry. Unfortunately, internal insulation can significantly change the wall’s hygrothermal performance, resulting in a higher risk on frost damage, wood rot of embedded beam heads, etc. The application of hydrophobisation is often put forward as a potential measure to avoid moisture problems, though more research on the impact of hydrophobisation is still required. Thereto, the current paper presents the results of a field study on the hygrothermal performance of internally insulated masonry with embedded wooden beam heads, exposed to wind-driven rain. Both a vapour open capillary active and a vapour tight insulation system are studied. Mainly the moisture conditions near the back of the wooden beam head are found to be influenced by hydrophobisation, which lowers the relative humidity. Closer to the masonry’s interior surface, the choice of the insulation system also influences the results. In case of a well-applied hydrophobisation, overall, the vapour tight system shows a better performance than the capillary active vapour open system. An exception to this is found for the first months after applying the hydrophobisation and the insulation system, where a longer drying period is needed in case of the vapour tight system.